This invention relates generally to switching apparatus and more particularly to a disconnect switch and drive mechanism therefor particularly adapted for use with gas insulated power systems.
In recent years, there has come about a demand for a reduced-size substation. This demand on the part of public utilities has been met by gas insulated substation equipment. This type of substation equipment significantly reduces the space required by the high voltage value of substations rated, for example, 46 KV through 500 KV. Space reduction is accomplished by replacing the open-bus and the air-tight bushings with gas insulated bus filled, for example, with a highly insulating gas such as sulfur-hexafluoride gas at a pressure, for example of 45 pounds per square inch gauge, and thereby permitting the movement of electrical equipment very closely together.
This gas insulated substation equipment has many advantages, among which are: significant reduction in size requirements both in land area and overall height; added system reliability by eliminating the possibility of phase-to-phase fault, lightning strikes within the system, or contamination of insulators; reduced maintenance because the closed system is isolated from the environment; added personnel safety because all live parts are covered by grounded shields; and lower installation costs as compared with conventional or other types of power systems when the gas insulated modular approach is utilized.
The gas insulating system, as briefly described above, has additional design strategies, inasmuch as the high voltage equipment is compressed, so that both the space required and the total length of the bus is minimized. The power transformers may be located on outside corners so as to be capable of ready removable, and the location of cable potheads is flexible, with results that the system may be readily connected to overhead transmission lines.
It is desirable to provide a disconnect switch which will permit the isolation of certain sections of the gas insulated system. This disconnect switch must be as compact as possible, and must be capable of functioning in its installed environment. Because the switch must operate in a sealed environment, the number of elements penetrating to the outside must be minimized, to reduce the possibility of gas leakage. Since the switch must be compact, it follows that the switch drive mechanism should also be as compact as possible.